Gas blast circuit breaker



Dec. 22, 1942, a. w. WYMAN GAS BLAST CIRCUIT BREAKER BLAST EXI'IlUST GASPRESSURE Filed June 14, 1941 Inventor": Bryce W. Wyman,

His Attorney.

Patented Dec. 22, 1942 GAB BLAST CIRCUIT BREAKER Bryce W. Wyman, Yeadon,Pa., assignor to General Electric Company, a corporation of New YorkApplication June 14, 1941. Serial No. 893.128

scum.

My invention relates to gas blast circuit oreakers wherein the arc to beinterrupted is confined in an insulating structure and traversed by ablast at gas fiowing at high velocity under pressure. and has for itsprincipal obiect the provision of an improved method of operation of andstructural arrangement for. a circuit breaker of the aforesaid type sothat it is particularly adapted for interrupting heavy currentsthroughout a wide range oi line ,voltage.

Theinterruptlon oi heavy overload and short circuit currents at moderatevoltages, such as kv., has been efiiciently accomplished by across-blast type air circuit breaker wherein thearcisdrivenbyatransverseblastofgasinto an arc chute having insulatingbarriers or partitions extending edgewise to and transversely of thearcstream. The hot blast gasesfiowing from the region of arcing aredirected to exhaust through the chute passages defined by the aforesaidpartitions. Such a circuit breaker is housing I defining arcextinguishing structure in which are mounted for relative movement thedisclosed and claimed in application Serial No.

803,126 filed November 6', 1939, by D. 0. Prince et al. for "Circuitbreaking apparatus and method of operating the same" now Patent No.2,284,842 issued June 2, 1942 and assigned to the same assignee as thepresent invention. When this type circuit breaker is used forinterruptin'g power currents at appreciably higher voltages. such as 50kv., insulation diiiiculties appear and, instead of clearing thecircuit, the breaker may fail d to fiashover. s

In accordance with my invention, the desirable current interruptingcharacteristics oi the aforesaid cross-blast type breaker are retainedand the voltage range of the breaker is appreciably increased byincorporating in the circuit breaker structure auxiliary meansiorsubjecting the arc to a high velocity axial blast prior to completion ofthe breaker opening operation.

My invention will be more fully set forth in the following descriptionreferring to the accompanying drawing. and the features of novcity whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

Referring to the drawing, Fig. l is an elevational view in section of agas blast circuit breaker embodying my invention in an initial stage ofthe opening operation, and Fig. 2 is a similar view illustrating thefinal stage oi a high voltage circult interrupting operation.

The circuit breaker illustrated by way of example in Figs. 1 and 2comprises an insulating breaker contacts 2 and 8. The contact I. whichmay be of any suitable type, such as the resilient finger type, is shownas fixed in the housing and is connected to one line terminal oi thebreaker indicated at 2'. The contact, I is termed as a blade member andis reciprocally movable in the insulating housing with respect to thefixed contact I, and is electrically connected as indicated to the otherline terminal of the breaker at 8'. v

The contacts 2 and 3 are separable within a narrow slot-like passage 4in'the housing and this passage is arranged to be connected at one sideto a source of gas pressure indicated at I. and at the pposite side (torthe first part of the contact-opening movement) with 'an arc chute 8.

atmosphere at I. The hot blast gases fiowingfromtheregionoiarcingatlarecooiedby means of spaced metallic platesdisposed edgewisetothegasflowasindicatedatl. The insulating barrier I ispreferably composed of a vaporizable insulating material. such as hardfibre. that does-not lose its dielectric strength in the presence of theare. An arc chute of this character is disclosed and claimed in thePrince et al. application above-identified;

When the breaker is to be opened. the movable contact I is actuated bysuitable means (not shown) toward the left as.viewed in Fig. i so as toseparate item contact 2 and form an arc gap opposite the entrance of thechute I. At practically the same instant, the interrupting gas isadmitted under pressure by way of the conduit I to the passage 4 so thatthe resulting blast of gas necessarily traverses the are between thecontacts I and 3 and drives it sideward against the insulating barrier Ion its way to exhaust from the chute passage I. At this stage of theopening operation, the gas blast is eilective to interrupt very heavycurrents at the first current zero.

In the case of high voltage circuits and circuits having a high rate ofrise of recovery voltage. this interruption at the first current neromay not be permanent and the dielectric strength of the gap so formedbetween the contacts may be insuilicient to prevent voltage breakdownand reestablishment of arcing. This difilculty in clearing the circuitis overcome in accordance with my invention by connecting in shunt withThe chute t is provided with at least one insulating barrier orpartition I dividing the chuteintoblastpassagesthatareventedto thecontacts during the initial opening operation, and in series therewithfor the final interrupting operation an auxiliary gas blast circuitbreaker of the axial blast type, preferably in series with a resistance.

To this end, an auxiliary gas blast switch of the axial blast typegenerally indicated at i is disposed adjacent to the path of movement ofthe blade contact 3 so that the auxiliary switch Ill is in electricalcontact with the blade 3 during the initial part of the opening movementto shunt the original arc gap and is placed in series with the bladecontact and breaker terminals immediately upon interruption of the areat thefirst current zero in the chute 6. In a simplified arrangement,the auxiliary breaker l0 comprises a movable rod contact I i that isresiliently biased, such as by a spring l2, into sliding electricalcontact at H with the blade I. The rod contact H is also electricallyconnected through a flexible conductor I3 to a terminal indicated at H,which is in turn electrically connected through a resistance ii to thebreaker line terminal 2' as indicated at IS. The rod contact II isguided for reciprocal movement in a cylinder ll formed in the maininsulating housing and includes a piston l8 which functions both as aguide for the rod contact and as a valve for uncovering the blast ventport It leading from the cylinder H. The rod contact Ii is operablewithin a restricted nozzle-like passage 20 communicating with thecylinder I! located a short distance beneath the point of contactengagement with the blade 3.

From the above description, it will be seen that immediately uponinterruption of the main power are at a current zero in the chute 6, theauxiliary breaker l0 and the resistor'i5 are connected in series withthe breaker terminals 2' and 3".

' Accordingly, the current as reestablished after the current zerothrough this connection will be of decreased magnitude, and in additionthe power factor will be improved. Therefore, when the blade contact 3in continuing its opening movement uncovers the aforesaid nozzle passageand moves out of engagement with the rod contact ll of the auxiliarybreaker, the resulting arc, which is immediately drawn into therestricted nozzle 20 due to the action of blast pressure from 5 on thepiston II, is more readily extinguished by the high velocity constrictedaxial blast within the insulating nozzle as clearly indicated by Fig. 2.When theauxiliary breaker contact reaches the position shown by Fig. 2,the blast passage is is also uncovered so that the gas blast can sweepunhindered through and longitudinally of the arc path. This blast flowsthrough as well as longitudinally (or axially) of the arc stream and thearrangement avoids many of the insulation difliculties of other types ofgas blast breakers. The axial blast arrangement above described has beenfound to be particularly adapted for interrupting high voltage circuits,although it is not so well adapted as the cross blast type abovedescribed for interrupting heavy currents. Therefore by firstinterrupting the heavy current are momentarily at a current zero, atwhich time a. resistance is automatically inserted in the circuit, andthen by interrupting the reduced current in the manner above described,it will be seen that I provide means for interrupting high voltage powercircuits not heretofore provided in the known types of gas blastbreakers.

It will also be seen that the gas pressure within the nozzle passage iscaused to build up until the contact piston-valve it opens the blastexhaust vent. This increased gas pressure in the region of arcing is anadditional asset during the interruption operation since the dielectricstrength of the gas is thereby increased.

It should be understood that my invention is not limited to specificdetails of construction and arrangement thereof herein illustrated, andthat changes and modifications may occur to one skilled in the artwithout departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. A gas blast circuit breaker for high voltage power circuitscomprising contacts including a movable contact separable to form an arcgap, an arc chute having an entrance opposite the initially formed partof said gap, means for directing an interrupting blast of gas throughsaid initially formed part of the arc gap to drive the arc into saidchute for extinguishing it at 9. current zero, a resistance arranged tobe connected in shunt with said part of said gap whereby a reestablishedpower current is reduced, and. a separately operable auxiliary gas blastcircuit breaker connected in series with said resistance, said auxiliarybreaker having a blast operated movable contact coacting with theaforesaid movable contact to form an arc gap and having a nozzle-likearc interrupting passage for said last-formed arc gap, and means fordirecting a second gas blast into said nozzle-like passage axially ofthe are for finally interrupting the reduced current are therein.

2. A gas blast circuit breaker for high voltage power circuitscomprising relatively fixed and movable contacts separable to form anarc gap, an arc chute having an entrance opposite the initially formedpart of said gap, means for directing an interrupting blast of gasthrough and across said initially formed part of the arc gap to drivethe are into said chute for extinguishing it at a current zero, aresistance arranged to be connected in shunt with said part of said gapwhereby a reestablished power current is reduced, and a separatelyoperable auxiliary gas blast circuit breaker included in said shuntconnection having a separate movable contact operable in response to gaspressure to form a second arc gap, said auxiliary breaker having anozzle-like arc interrupting passage inwhich said second arc gap isformed, and means for directing a second gas blast into said nozzle-likepassage axially of the are for finally interrupting the reduced currentarc therein, said second gas blast also being effective to build uppressure in said passage to cause opening movement of said movableauxiliary breaker contacts.

3. A gas blast circuit breaker for high voltage power circuitscomprising relatively movable contact structure separable to form an arcgap, an arc chute having insulating partitions forming arc barriers andhaving an entrance opposite an initially formed part of said gap, meansfor directing an interrupting blast of gas transversely through saidinitially formed part of the arc gap so as to drive the are into saidchute against said barriers for extinguishing the are at a current zero,a resistance arranged to be connected in shunt with said part of saidgap whereby a reestablished power current is reduced, and a separatelyoperable auxiliary gas blast circuit breaker included in the resistanceshunt connection and having a movable contact arranged to makeelectrical contact with the aforesaid relatively movable contactstructure so as to form a second arc gap only after predeterminedseparation 01' said contact structure, said auxiliary breaker having anozzle-like arc interrupting passage through which said auxiliarycontact is movable and in which said second arc gap is formed, and meansfor directing a second as blast into and through said nozzle-likepassage 5 the reduced current are.

BRYCE W. WYMAN.

